1. Field of the Invention
The present invention relates to a display device provided with a touch panel. The invention more particularly relates to a display device provided with a touch panel arranged on a front surface of a display panel, with the touch panel having a structure in which electrodes intersect with each other.
2. Description of the Related Art
Display devices, such as a liquid crystal display device or an organic electroluminescent (EL) display device, are used for electronic devices such as a mobile phone, a car navigation system, a camera, an automatic ticket machine, and an ATM terminal. In addition, a display device provided with a touch panel has widely been used in recent years, as illustrated in FIG. 1. This display device has a touch panel (TP) arranged on the front surface of a display panel (DP) through an adhesion layer (AD) provided therebetween. In operation, a user enters information corresponding to an image being displayed by touching the touch panel with a finger or a touch pen while referring to the image displayed on the display panel.
Such touch panels include a resistance film touch panel, a capacitive touch panel, and the like. In the capacitive touch panel, a transparent conductive film is formed on a glass substrate and electrodes are extended in directions intersecting with each other, so that an input position is detected in a manner which detects a change in capacitance between the electrodes when a finger or the like touches the capacitive touch panel.
A capacitive touch panel as described above is described in JP-2010-9439-A. The touch panel described in JP-2010-9439-A also has a structure in which X electrodes intersect with Y electrodes; however, this type of touch panel possess a problem as follows. When the touch panel is used outdoors or in an environment where irradiation light is strong, part of the intersecting portions of the electrodes will reflect light and shine because of the structure of the intersecting portion of the electrodes, thereby reducing the visibility of an image.
The aforementioned problem is described in detail with reference to FIGS. 2 and 3.
FIGS. 2 and 3 are plan views (on upper sides of FIGS. 2 and 3) of electrode structures used in conventional touch panels and cross-sectional views (on lower sides of FIGS. 2 and 3) taken along alternate long and short dash lines A-A′ of the plan views. In each of the conventional touch panels, an X electrode EX extending in X direction and a Y electrode EY extending in Y direction are formed on a transparent substrate 1. Although FIGS. 2 and 3 each illustrate only an intersecting portion of the X and Y electrodes, patterns that are the same as the pattern illustrated are continuously formed on the upper, lower, left, and right sides of each in FIGS. 2 and 3.
A transparent electrode 3 (13) that constitutes the X electrode EX and the Y electrode EY and is made of ITO, IZO, or the like is formed on the transparent substrate 1 made of glass or the like. At a portion at which the X electrode EX intersects with the Y electrode EY, the transparent electrode 3 (13) of either one of the X electrode EX or the Y electrode EY is continuously formed, and that of the other one of the electrode EX or EY is discontinuously formed. FIGS. 2 and 3 each illustrate an example in which the transparent electrode 3 (13) constituting the X electrode EX is discontinuously formed.
In order to electrically connect the parts of the transparent electrode 3 (13) at a discontinuous portion, a connecting electrode 2 (10) formed of a transparent conductive film made of ITO or the like is arranged. At the portion at which the X electrode EX intersects with the Y electrode EY, an interlayer insulating film 4 (14) is arranged between the connecting electrode 2 (10) and the transparent electrode 3 (13) constituting the Y electrode EY. In FIG. 2, an upper bridge structure is illustrated, in which the connecting electrode 2 is arranged on the interlayer insulating film 4, and the parts of the transparent electrode 3 at the discontinuous portion, which constitute the X electrode EX, are electrically connected to the connecting electrode 2 in a region denoted by reference numeral 7. In FIG. 3, a lower bridge structure is illustrated, in which the connecting electrode 10 is arranged under the interlayer insulating film 14, and the parts of the transparent electrode 13 at the discontinuous portion, which constitute the X electrode EX, are electrically connected to the connecting electrode 10 in a region denoted by reference numeral 7.
Reference numeral 6 denotes an index matching layer to be used to visually recognize the transparent electrode 3 (13) made of ITO or the like and the connecting electrode 10. Reference numeral 9 denotes a protective film for protecting the X electrode and the Y electrode. Reference numeral 5 denotes a transparent conductive film made of ITO or the like and arranged on a back surface of the transparent substrate 1.
If the upper bridge structure illustrated in FIG. 2 is used, since the parts of the transparent electrode 3 constituting the X electrode EX are connected to the connecting electrode 2 in the connection region 7, the interlayer insulating film 4 has a contact hole in the connection region 7. The contact hole is formed in a substantially trapezoidal shape as shown in the plan view of FIG. 2. As illustrated in the cross-sectional view of FIG. 2, the connecting electrode 2 is arranged along a side surface forming the contact hole of the interlayer insulating film 4 and therefore inclined along the side surface of the interlayer insulating film 4. As a result, a portion 8 surrounded by a solid line in the plan view of FIG. 2 is made shine by the reflecting outside light and causes a reduction in the visibility of an image.
If the lower bridge structure illustrated in FIG. 3 is used, the transparent electrode 13 is formed so as to cover the interlayer insulating film 14. The interlayer insulating film 14 is traditionally formed in a substantially rectangular shape as illustrated in the plan view of FIG. 3. Similarly to FIG. 2, the transparent electrode 13 is arranged along a side surface of the interlayer insulating film 14 and inclined along the side surface of the interlayer insulating film 14 as illustrated in FIG. 3. As a result, a portion 8 surrounded by a solid line illustrated in the plan view of FIG. 3 is made shine by reflecting outside light and causes a reduction in the visibility of an image.